Fluid-blast circuit interrupter with improved current-transformer housing means



1963 G. J. EASLEY ETAL 3,114,315

FLUID-BLAST CIRCUIT INTERRUPTER WITH IMPROVED CURRENT-TRANSFORMERHOUSING MEANS Filed Nov. 18, 1959 5 Sheets-Sheet 1' INVENTORS Robert L.Hess, James M. elford and Gilbert J. Eosley BY W m E W ATTORNEYWlTNiZS/MH W 93? Dec. 17, 1963 G. J. EASLEY ETAL 3, 5 FLUID-BLASTCIRCUIT INTERRUPTER WITH IMPROVED CURRENT-TRANSFORMER HOUSING MEANSFiled Nov. 18, 1959 5 Sheets-Sheet 4 Fi .5. 8 9 g as O 86 Dec. 17, 1963G. J. EASLEY ETAL 3,114,815

FLUID-BLAST CIRCUIT INTERRUPTER WITH IMPROVED Filed Nbv. 18, 1959CURRENT-TRANSFORMER HOUSING MEANS 5 Sheets-Sheet 5' United States PatentFLUID-BLAST CIRCUIT INTERRUPTER WITH IM- PROVED CURRENT-TRANSFORMERHOUSING MEANS Gilbert 3. Easley, Edgewood Borough, Robert L. Hess, NorthVersailles Township, Allegheny County, and James M. Telford, Penn HillsBorough, Pa., assignors to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Filed Nov. 18, 1959, Ser.No. 853,974 4 Claims. (Cl. 200-148) This invention relates tofluid-blast circuit-interrupters, in general, and, more particularly, toimproved arcextinguishing structures, mounting arrangements andourrent-transformer housing means therefor.

In :United States patent application filed September 15, 1959, SerialNo. 840,133, by Robert E. Friedrich, Carl G. Lentjes, and George B.Cushing, and assigned tothe assignee of the instant application, thereis disclosed and claimed a fluid-blast circuit-interrupter of the puffertype, in which a relatively movable operating cylinder, carrying themovable contact structure, slides axially over a stationary hollowinsulating pedestal having a relatively fixed piston attached thereto,to compress gas, and to force the compressed gas through an orificestructure to effect extinction of the are drawn between the relativelymovable contact and a cooperabl-e stationary contact. It is a generalobject of the present invention to improve upon the circuit-interruptingstructure of the aforesaid application, rendering the same particularlysuitable for a simplified mounting construction, eliminating theterminal bushing, and employing a pair of current-transformerstructures, between which any internal fault current flows to ground toobtain overlapping relay protection.

Another object of the present invention is to provide an improvedsimplified, puffer-type, circuit-interrupting structure, in which thenumber of parts are kept to a minimum, and assembly and disassemblyoperations are readily achieved.

Another object of the present invention is to provide an improvedcurrent-transformer arrangement, in which an insulating shield isemployed to prevent the currenttransformer being surrounded by ashort-circuited turn of metal.

Another object of the present invention is to provide an improvedfluid-blast-type of circuit-interrupter in which a pair of spacedcurrent-transformers are arranged so that any fault occurring within thecircuit-interrupting structure will pass to ground between the twocurrenttransformers, and be reflected as an internal fault, causingthereby the tripping not only of the circuit-interrupter itself, butalso the tripping of the remote circuit breakers connected to theconsidered circuit breaker.

Another object of the present invention is to provide an improvedelongated circuit-interrupting structure in which the guiding functionsfor the movable contact assembly are facilitated, and the resultingstructure is trouble-free in operation.

Yet a further object of the present invention is to provide an improvedcircuit-interrupter of the putier type, which is particularly suitablefor the use of a high-dielec trio-strength, effective, arc-extinguishingfluid, such as sulfur hexafluoride (SP Still a further object of thepresent invention is to provide an improved fluid-blastcircuit-interrupter in which improved crank means are employed to effectthe axial opening movement of the movable contact structure.

Another object of the present invention is '00 provide an improvedcircuit-interrupter in which the servicing and maintenance operationsare readily achieved by the removal of only a few parts.

ICE

Another object of the present invention is to provide an improvedsimplified type of circuit-interrupter in which the movable contactstructure, and the guiding support therefor, may readily be removed outof one end of the circuit-interrupting structure with a minimum ofdisassembly of parts.

Another object of the present invention is to provide an improvedcircuit-interrupter in which the adjustment of the parts is readilyachieved.

Another object of the invention is to provide an improvedgaseous-type ofcircuit-interrupter in which the enclosed gas is not only employed tocreate an arcextinguishing blast of gas, but is also utilized as agaseous dielectric medium between the high-voltage parts of the breakerand the grounded interrupter housing. As a result, a terminal-bushingconstruction is not necessary with associated organic insulation, whichis subject to aging and possible eventual failure over a period ofyears.

'Further objects and advantages will readily become apparent uponreading the following specification, taken in conjunction with thedrawings, in which:

FIGURE 1 is a front elevational view of a three-polecircuit-interrupting assemblage embodying the principles of the presentinvention;

FIG. 2 is a side elevational view of the circuit-interrupting assemblageof FIG. 1;

FIG. 3 is a fragmentary, enlarged, longitudinal, vertical sectional viewtaken through one of the three areextinguishing pole units, with thecontact structure being illustrated in the closed-circuit position;

FIG. 4 is a similar fragmentary, longitudinal, vertical sectional viewtaken through the other end of the pole unit of FIG. 3, but illustratingthe position of the contacts in the fully open-circuit position;

FIG. 5 is a ventical sectional view taken along the line V-V of FIG. 3;

FIG. 6 shows schematically the association with a single pole unit ofremote protective circuit breakers and a differential protectiverelaying scheme for distinguishing between internal and external faultsoccurring at the pole unit; and,

FIG. 7 illustrates a modified type of current transformer mountingarrangement to reflect porcelain flashover faults associated with thecircuit-interrupter as external faults, as contrasted with internalfaults.

Referring to the drawings, and more particularly to FIGS. 1 and 2thereof, the reference numeral lgenerally designates a three-polecircuit-interrupting assemblage, which is mounted at the upper end of aframe support 2, the latter being welded to angle feet 3, which may restupon a suitable base. The reference letters A, B and C designate thethree individual circuit-interrupting pole units, which are allidentical in construction and opera tion.

FIG. 2 shows more clearly how the three circuit-interrupting pole unitsA, B and C, constituting a three-phase circuit-interrupter, are mountedat the upper end of the frame support 2. The frame support 2 preferablyincludes a pair of upstanding channel members 4, which have cross-braces5, 6 welded thereacross. Disposed between the uprights 4, and positionedbetween the cross-braces 5,

'6 is a mechanism compartment 7, housing a suitableoperating mechanism,which effects simultaneous opening and closing movement of threeidentical pole units A, Band C of the circuit-interrupting assemblage 1.

A rotatable operating shaft 8 mechanically interconnects the three poleunits A, B and C. As well known by those skilled in the art, a crank-armassembly 11 (FIG. 5) is employed within a compartment 9 (FIG. 1) and ispivotally connected to a pull-rod extending downwardly within anenclosing tube 10 to be connected to the operating mechanism enclosedwithin the mechanism compartment 7. Generally, the actuating mechanismdisposed within compartment 7 may be of any suitable type, and isoperated to effect upward thrusting motion of the operating rod withinthe tube 10 during the opening stroke. This action is facilitated byopening accelerating springs, not shown, also disposed within thevertical housing tube 10. A suitable operating mechanism, not shown, isprovided to effect the closing of the circuit-interrupter and a chargingof the aforesaid accelerating spring.

The operating mechanism may be of any desired type such as pneumatic,hydraulic, or may comprise a solenoid for effecting downward closingmotion of the operating rod disposed within enclosing tube 10.

With reference to FIG. 5, it will be noted that the rotatable operatingshaft 8 is keyed to an internally disposed operating crank-arm 12, whichis welded to a forked member 13. The ends of the furcations, or arms 14,of the resulting bifurcated crank-arm construction are pivotallyconnected by pins 14a, 15a (FIG. 3) to links 16 disposed externally of amovable puffer cylinder 17. Jutting laterally outwardly fromdiametrically opposite sides of the puffer cylinder 17 are a pair ofpivot pins 17a to which the driving links 16 are connected. Thus, asviewed in FIG. 4, the counterclockwise rotation of the operating shaft 8is effective to force the links 16 toward the left, and to effectleftward working motion of the operating puffer cylinder 17 over astationary piston 18 secured to the right-hand end of a hollowinsulating guide tube, or pedestal 19. As shown, the hollow insulatingguide tube 19 is threadedly secured, as at 20, to a collar 21, which issecured to an annular mounting plate 22, the latter being bolted, bybolts 23, to a closure plate, or combined end support plate 24 of agrounded interrupter housing, generally designated by the referencenumeral 25.

As illustrated in FIG. 3, the operating cylinder 17 carries a movablecontact support 26, the latter having integrally formed movable maincontact fingers 27 and is secured, by a stud portion 360, of guide rod36, to a centrally-located movable arcing electrode 28. The movablearcing electrode 28 engages within a hollow portion 29 of a relativelystationary rod-shaped contact 30.

The relatively stationary rod-shaped contact 30 is fixedly secured, asat 31, to a conducting support tube 32, the latter being adjustablysecured within a mounting boss 33, disposed at the right-hand end of thecircuit-interrupting pole unit.

It will be noted that jutting outwardly in opposite directions from thecentrally disposed interrupter housing are a pair of identicalinsulating casings 34, preferably composed of a suitable Weather-proofmaterial, such as porcelain. Corrugations 35 may be formed along theexternal surface of the porcelain casing 34 for providing an increasedsurface breakdown path.

As shown in FIG. 3, it will be observed that the movable contact support26 is threadedly secured, by the stud portion 36a, to the conductingguide rod 36, which is guided at its left-hand end, as viewed in FIG. 4,by a plurality of resilient fingers 37, which carry current therefrom toa terminal plate 38.

The terminal plate 38 is fixedly secured by bolts 39 to an annularmounting flange 40, cemented to the left-hand end of the left-handporcelain casing 34. The right-hand end of the left-hand casing 34similarly has cemented thereto an annular mounting flange 41, which isbolted by bolts 42 to the closure plate 24 of the interrupter housing25.

A pair of current-transformers 43, 44 are provided in spaced relationexternally of the tubular portion 45 of the grounded interrupter housing25. They are so arranged that any internal breakdown, or internal faultcondition occurring within the circuit-interrupter pole unit will passto ground between them, to be reflected as an internal fault condition,and, consequently, will result in a tripping of the remote circuitbreakers 46, 47, respectively connected, by line connections 48, 49 tothe terminals 50, 51

as more clearly shown in FIG. 6 of the drawings. Thus, the line L passesthrough the circuit breaker 46, the circuit-interrupter pole unit, andthrough the other remote circuit breaker 47 to the remote line LCurrent-transformers 52, 53 are associated with the lines L L andmeasure the current passing through circuit-interrupters 46, 47,respectively.

A pair of differential protective relays 54, 55 are provided, theirwindings being connected in parallel with the secondary windings of thecurrent-transformers 52, 44 and 43, 53, respectively, as illustrated inFIG. 6 of the drawing.

When the differential relay 54 picks up to close the bridging contact 56across the stationary contacts 57, a tripping circuit 53 is made up, toenergize the coil 59 of a tripping magnet 60, which releases a latch 61to permit opening of the movable bridging contact 62 of the remotecircuit-interrupter 46.

Tripping the circuit-interrupter 46 open results in the opening of anauxiliary set of contacts 63, which deenergizes the tripping circuitthrough coil 59. As shown in FIG. 6, the tripping circuit 58 alsoenergizes a solenoid 64 to move an armature 65 upwardly, which resultsin releasing the latch 66 to permit opening of the circuitinterruptingpole unit 1. More specifically, an operating rod 67 is shown as beingbiased in an opening direction by an accelerating spring 67a to effectopening, rotative counterclockwise motion of the operating shaft 8. Upontripping the breaker, the winding 64 is de-energized by the opening of aset of contacts 71, which open upon opening motion of thecircuit-interrupter pole unit.

Similarly, the differential relay 55 is operative to pick up a bridgingcontact 72, which bridges a pair of stationary contacts 7'3, and makesup a tripping circuit 74. The tripping circuit 74 energizes a tripwinding 75, which moves an armature '76 upwardly and releases a latch 77to effect opening of the remote circuit-interrupter 47.

The opening of the circuit-interrupter 47 results in downward movementof an operating rod 78 associated therewith which effects opening of anauxiliary bridging contact 79 from a pair of stationary contacts 80 todeenergize the winding 75.

In addition, the tripping circuit 74 also energizes a coil 81, whichreleases the latch 66 in a manner as pre viously explained, to effectopening of the circuit-interrupter pole unit. Auxiliary contacts 82,associated With the operating rod 67 of the circuit-interrupter poleunit, effect, upon opening of the circuit-interrupter pole unit,de-energization of the tripping solenoid 81.

Should an external fault condition occur from the line 48 to ground 68,as indicated by the reference numeral 83, and assuming that the currentflows from the line L toward the line L it will be obvious to thoseskilled in the art that only the differential relay 54 is picked up, thedifferential relay 55 remaining de-energized. The result of theforegoing condition is that only the circuitinterrupter pole unit andinterrupter 46 are opened, with the remote circuit-interrupter 47remaining closed, which is desirable.

If the current flows from the direction of the line L toward the line Land a fault condition occurs externally of the circuit-interrupter poleunit, as at the location 83, again the differential relay 54 will bepicked up by the measurement of current from the current transformer 44,and no current being indicated in the secondary winding of thecurrent-transformer 52. On the other hand, since the current-transformerwindings 43, 53 measure the same fault current, the differential relay55 will not be picked up. Similar conditions would arise should anexternal fault take place at the location 84, that is, opening of onlyone differential relay, this time differential relay 55, differentialrelay 54 remaining deenergized. As a result of this action, only thecircuitinterrupters 1 and 47 would open, circuitinterrupter 46 remainingclosed, which is desirable.

Assume, however, that an internal fault condition takes place, such asdesignated by the reference numeral 69 in FIG. 3, or 70 in FIG. 5, whichthe breaker 1 is unable itself to clear. As mentioned previously, thefault current in such cases will flow to ground 68, (FIG. 1) between thetwo current-transformers 43, 44. This arises because of the fact thateach of the current-transformers 43, 44 has an external insulating cover43a and 4411, which compels any fault current, such as the fault current69 to flow to ground 68 between the two currenttransformers 43, 44. Aswell known to those skilled in the art, such a passage of fault currentbetween the two current-transformers 43, 44 will effect the energizationof both differential protective relays 54, 55, regardless of thedirection of current flow, and will, consequently result in the trippingof all the breakers, namely, circuitinterrupters 1, 46 and 47.

Reference may be had to United States patent application filed March 31,1958, Serial No. 725,286, now United States Patent 3,032,689, issued May1, 1962, to Benjamin P. Baker and Robert F. Karlicek, and assigned tothe assignee of the instant application, for a theoretical discussion ofoverlapping differential protective relay operation in distinguishingbetween external faults, which the breaker can clear, and internalfaults, which the breaker cannot clear and require opening of bothremote breakers.

By Way of retrospect, during the opening operation, the mechanismdisposed interiorly within the mechanism compartment 7 is effective tocause, through the linkage disposed within enclosing tube 10, rotativeopening movement of the operating rod 8 and extending between the threepole units A, B and C.

The counterclockwise rotative opening motion of the operating shaft 8,as viewed in FIGS. 2 and 3, is transmitted interiorly of the interrupterhousing by way of gas-tight seals 86 (FIG. to effect counterclockwise,rotative, opening motion of the bifurcated crank-arm 12.

As viewed in FIG. 3, the counterclockwise opening rotative motion of thebifurcated crank-arm 12 results, through the linkage 16, in leftwardopening movement of the outer operating puffer cylinder 17 over theinner stationary tubular pedestal 19, which supports the fixed piston18. The result of this relative movement is compression of a suitablearc-extinguishing fluid, such as sulfur hexafiuoride (SP gas, within thecompression chamber 87 (FIG. 3). The raising of the gas pressure withinthe compression chamber 87, defined by the operating puffer cylinder 17and the stationary piston 18, results in the ejection of compressedarc-extinguishing gas past the movable contact support 26, and outthrough the orifice 88, carried by the movable puffer cylinder 17, asindicated by the arrows 85 in FIG. 4.

A l-though FIG. 4 shows the fully open-circuit position of thecircuit-interrupter 1, nevertheless, for purposes of illustration, theestablished are 95 has been indicated as well as the direction of thefluid blast.

The contact fingers 27 first separate from the outer sides 30a of thetip portion of the stationary rod contact 30, and subsequently thearcing electrode 28 moves out of the recess 29 to effect drawing of theare 95 between the tip extremity 28a and the arc-resisting stationaryring portion 89' of the stationary rod contact 30. This are 95, shown inFIG. 4, is blasted by a flow of compressed sulfur-hexafiuoride gasissuing from the compression chamber 87 and passing through the orifice88. Arc-extinction rapidly follows, and in the fully open-circuitposition of the interrupter 1, as indicated in FIG. 4, the position ofthe several parts is such that a stationary rod contact 30* is disposedexternally of the movable orifice 88.

It will be observed that during the opening motion, the puffer cylinder17 is guided over the stationary inner pedestal tube 19. In addition,the guide rod 3 6, movable with the movable contact structure, is guidedby the guide and contacting fingers 37, shown in FIG. 4.

During the closing operation, the operating shaft 8, as viewed in FIG.3, is rotated in a clockwise direction. This effects through the linkage16, rightward closing travel of the outer pufier opera-ting cylinder 17and movable contact structure to result in closing of the contactstructure, and a drawing of compressed gas from the region '90 into theregion 87 interiorly of the operating cylinder 17; Since this is freshgas and is uncontaminated, the interrupter 1 is in a suitable conditionfor a subsequent reopening operation, if this is necessary.

The circuit-interrupting structure 1, disclosed in FIG. 3, isparticularly suitable for a moderate-rating circuitinte-rrupter, sayoperable on a circuit extending up, say, through 69 kv. By employingsuitable dimensions higher voltages may be interrupted, and it is to beunderstood that the invention is not restricted to the lower voltages.Merely for purposes of illustration is the invention shown applied to a46 kv. circuit-interrupter. Preferably, an effective arc-extinguishingfluid or gas, such as sulfur hexafiuoride (SP gas, at severalatmospheres pressure, is disposed interiorly within the interruptingunit. The puffer-type interrupter, which is employed, is highlyeffective and is simple in operation. The sulfur hexafluoride (SP gas isused for both the dielectric medium and for the interrupting medium. Itis to be noted that the present interrupter has a centrally disposed,grounded interrupter housing 25 with symmetrical, identical, gasfilledporcelains 34 to form the bushings. In addition, it is to be noted thatthe current-transformers 43, 44 are disposed outside of the casing 25,defined partially by the tubular portion 45, and use an insulated cover43a or 44a for the outside transformer casings to prevent thecurrent-transformers 43, 44 being surrounded by a shortcircuited turn ofmetal. Being isolated from the pressure tank 25 eliminates the need forgas-tight seals for leads for connection to the current-transformers 43or 44.

The outer operating cylinder 17, being connected to the operating lever12 by means of the connecting rod links 16, perm-its the interrupter 1to be disconnected from the operating lever 12 when the bushing casing34 is removed from the left-hand end of the interrupter housing 25.

Relatively stationary contact adjustment is made by turning a threadedstationary contact rod 32, as at 32a, within the mounting boss 33. Thismay be done, of course, following removal of the cover plate 91following unscrewing of the bolts 92.

A particular advantage of the circuit-interrupting assemblage -1 is thatthe mechanism compartment 7 hang-s under the circuit-interrupter, makingthe whole unit adaptable for either pole or frame mounting.

A valve assembly may be associated with the grounded interrupting casing25 to feed sulfur-hexafluoride (SP gas into the interrupter casing. Apressure gauge 94 may be employed which is visible downwardly so that astation attendant may check the pressure conditions within theinterrupter casing. A low-pressure switch 96 may be utilized to effectopening of the interrupter -1 upon the occurrence of low-pressureconditions, or to sound an alarm.

A rupture diaphragm 9111 may be employed to rupture upon excess pressuredue to an internal fault and thereby prevent shattering of the porcelaincasings 34. An act'- vated alumina getter may be used to absorb moistureand decomposed are products.

From the foregoing description, it will be apparent that there has beenprovided an improved, simplified type of circuit-interrupter embodyingfew parts, which may be readily assembled and disassembled.Accessibility for service and maintenance is provided, it merely beingnecessary to remove one of the two porcelain casings 34 from the endplates 24, 93 of the interrupter housing 25. By employing a rotatableoperating shaft 8, the gas-tight 7 seals 86, illustrated in FIG. 5, aresmall and compact. Such ring-type seals 86 have proved, in practice, tobe highly effective.

It will be noted that no terminal bushing, having organic insulation, isemployed which might age and deteriorate through years of service. Theenclosed gaseous medium, such as sulfur hexafiuoride, is used not onlyfor an effective arc-extinguishing blast of gas but also for dielectricstrength between the high-voltage parts and the outer groundedinterrupter casing 25. It is self-healing in the event of breakdown.

FIG. 7 illustrates a modified current-transformer mounting arrangementin which the surrounding currenttransformers 98, 99 are surrounded by aconducting shield 100. The shield 100 may be welded, as at 101, to amounting flange 102. Bolts 103 and nuts 1.04 clamp a second mountingflange 105 intoposition, the latter being cemented at 106 to theleft-hand end of the insulator 34.

The current-transformer mounting arrangement, illustrated in FIG. 7, issuitable for those utility customers who desire all porcelain casingflash-over faults associated with the circuit-interrupter 1 to bereflected as external faults, as contrasted with internal faults. Anyfault current, such as represented by the fault condition 107, flashingover the surface 188 of the porcelain casing 34 on one side of thebreaker 1, will pass to ground independently of the current-transformers98, 99. Since currenttransformers 98, 99 are unaffected by such a faultcondition 107, only a single remote breaker, such as breaker 47 on thesame side of breaker 1, is aifected together with thecircuit-interrupter 1. The other remote breaker 46 on the other side ofbreaker 1 remains closed, which may be desirable in some circumstances.

In a similar manner, a flashover 108 on the other side of breaker 1, asindicated in FIG. 7, will cause opening only of breaker 1 and remotebreaker 46, the breaker 47 remaining closed.

Thus the circuit-interrupter of the present invention may be arranged tohave all faults associated therewith reflected as internal faults toopen all breakers 1, 46, 47 by the arrangement according to FIG. 6. Or,as mentioned, where it is desirable to prevent opening of the remotebreakers 46, 47 as much as possible, then the current-transformerarrangement of FIG. 7 may be employed, where interrupter 1 and only oneof the two remote breakers 46, 47 open, keeping the rest of the systemconnected.

Although there have been shown and illustrated particular types ofcircuit-interrupting structures, it is to be clearly understood that thesame were merely for the purpose of illustration, and that changes andmodifications may readily be made therein by those skilled in the art,without departing from the spirit and scope of the invention.

We claim as our invention:

1. A fluid-blast circuit-interrupter including an upright grounded framesupport, a cylindrically-shaped, horizontally-extending, grounded,metallic interrupter housing extending substantially at right angles tosaid upright frame support and supported thereby, a pair ofoppositely-extending insulating hollow cylindrical casings secured toopposite ends of said cylindrically-shaped interrupter housing, a lineterminal disposed at the outer end of each horizontally-extendinginsulating casing, a pair of spaced current-transformers surrounding thegrounded interrupter housing and supported thereby and having outer atleast partially insulated concentrically-arranged currenttransformerhousing means so that any fault condition associated with thecircuit-interrupter will pass to ground between the twocurrent-transformers and be reflected as an internal fault condition,said current-transformer housing means including as an inner portionthereof said metallic interrupter housing, an end support plate closingone end of said current-transformer housing means and disposed adjacentone end of the metallic interrupter housing, a stationaryhorizontally-extending pedestal guide cylinder having a fixed pistonsecured adjacent one end thereof and disposed substantiallyconcentrically within said cylindrically-shaped metallic interrupterhousing, means securing said guide cylinder adjacent the other endthereof to said end support plate so that upon removal of the endsupport plate from the metallic interrupter housing the pedestal guidecylinder will be removed therewith as well as exposing saidcurrent-transformer housing means, a movable operating puffer cylindercarrying a movable contact and orifice slidable over saidhorizontally-extending guide cylinder and guided thereby, a rodshapedstationary contact extending along one of said hollow insulating casingsinteriorly thereof and cooperable with said movable contact, areciprocally movable conducting guide rod connected to said movablecontact and extending through the other hollow cylindrical casing, andguiding current transfer means conductively engaging the outer portionof said guide rod to transfer current therefrom to the respective lineterminal, whereby upon removal of said end support plate exposing saidconcentrically-arranged current-transformer housing means the pedestalguide cylinder, puffer operating cylinder, and movable contact will beremoved therewith for inspection and possible replacement.

2. The combination of claim 1, wherein the hollow casings and theinterrupter housing are filled with a highdielectric-strength gascomprising sulfur hexafluoride (SP6)- 3. The combination of claim 1,wherein rotatable operating crank means extending within the interrupterhousing are employed to effect reciprocal movement of the pufferoperating cylinder.

4. The combination of claim 1, wherein the currenttransforrner housingmeans includes a separate spaced housing for each of two currenttransformers and each housing has an end plate associated therewith.

References Cited in the file of this patent UNITED STATES PATENTS2,788,418 Owens et al. Apr. 9, 1957 2,804,576 Coggeshall et al Aug. 27,1957 2,866,045 7 Leeds Dec. 23, 1958 FOREIGN PATENTS 599,970 GreatBritain Mar. 25, 1948 477,005 Great Britain Dec. 20, 1937 1,146,902France May 27, 1957

1. A FLUID-BLAST CIRCUIT-INTERRUPTER INCLUDING AN UPRIGHT GROUNDED FRAMESUPPORT, A CYLINDRICALLY-SHAPED, HORIZONTALLY-EXTENDING, GROUNDED,METALLIC INTERRUPTER HOUSING EXTENDING SUBSTANTIALLY AT RIGHT ANGLES TOSAID UPRIGHT FRAME SUPPORT AND SUPPORTED THEREBY, A PAIR OFOPPOSITELY-EXTENDING INSULATING HOLLOW CYLINDRICAL CASINGS SECURED TOOPPOSITE ENDS OF SAID CYLINDRICALLY-SHAPED INTERRUPTER HOUSING, A LINETERMINAL DISPOSED AT THE OUTER END OF EACH HORIZONTALLY-EXTENDINGINSULATING CASING, A PAIR OF SPACED CURRENT-TRANSFORMERS SURROUNDING THEGROUNDED INTERRUPTER HOUSING AND SUPPORTED THEREBY AND HAVING OUTER ATLEAST PARTIALLY INSULATED CONCENTRICALLY-ARRANGED CURRENTTRANSFORMERHOUSING MEANS SO THAT ANY FAULT CONDITION ASSOCIATED WITH THECIRCUIT-INTERRUPTER WILL PASS TO GROUND BETWEEN THE TWOCURRENT-TRANSFORMERS AND BE REFLECTED AS AN INTERNAL FAULT CONDITION,SAID CURRENT-TRANSFORMER HOUSING MEANS INCLUDING AS AN INNER PORTIONTHEREOF SAID METALLIC INTERRUPTER HOUSING, AN END SUPPORT PLATE CLOSINGONE END OF SAID CURRENT-TRANSFORMER HOUSING MEANS AND DISPOSED ADJACENTONE END OF THE METALLIC INTERRUPTER HOUSING, A STATIONARYHORIZONTALLY-EXTENDING PEDESTAL GUIDE CYLINDER HAVING A FIXED PISTONSECURED ADJACENT ONE END THEREOF AND DISPOSED SUBSTANTIALLYCONCENTRICALLY WITHIN SAID CYLINDRICALLY-SHAPED METALLIC INTERRUPTERHOUSING, MEANS SECURING SAID GUIDE CYLINDER ADJACENT THE OTHER ENDTHEREOF TO SAID END SUPPORT PLATE SO THAT UPON REMOVAL OF THE ENDSUPPORT PLATE FROM THE METALLIC INTERRUPTER HOUSING THE PEDESTAL GUIDECYLINDER WILL BE REMOVED THEREWITH AS WELL AS EXPOSING SAIDCURRENT-TRANSFORMER HOUSING MEANS, A MOVABLE OPERATING PUFFER CYLINDERCARRYING A MOVABLE CONTACT AND ORIFICE SLIDABLE OVER SAIDHORIZONTALLY-EXTENDING GUIDE CYLINDER AND GUIDED THEREBY, A RODSHAPEDSTATIONARY CONTACT EXTENDING ALONG ONE OF SAID HOLLOW INSULATING CASINGSINTERIORLY THEREOF AND COOPERABLE WITH SAID MOVABLE CONTACT, ARECIPROCALLY MOVABLE CONDUCTING GUIDE ROD CONNECTED TO SAID MOVABLECONTACT AND EXTENDING THROUGH THE OTHER HOLLOW CYLINDRICAL CASING, ANDGUIDING CURRENT TRANSFER MEANS CONDUCTIVELY ENGAGING THE OUTER PORTIONOF SAID GUIDE ROD TO TRANSFER CURRENT THEREFROM TO THE RESPECTIVE LINETERMINAL, WHEREBY UPON REMOVAL OF SAID END SUPPORT PLATE EXPOSING SAIDCONCENTRICALLY-ARRANGED CURRENT-TRANSFORMER HOUSING MEANS THE PEDESTALGUIDE CYLINDER, PUFFER OPERATING CYLINDER, AND MOVABLE CONTACT WILL BEREMOVED THEREWITH FOR INSPECTION AND POSSIBLE REPLACEMENT.